1. Field of the Invention
The present invention relates to a mounting for a transmitter or a receiver, in particular to a mounting for a magnetic or aerial coil. Mountings in accordance with preferred embodiments of the invention may be useful in devices used to stimulate muscles in the human body, for example devices used in the treatment of foot-drop.
2. Description of the Related Art
Many patients who have suffered a stroke or other conditions, for example dorsiflexor injuries, peripheral nerve injuries, neuropathies, drug toxicities or diabetes, suffer from foot-drop. Foot-drop (or dropfoot) is an inability to lift the front of the foot (dorsiflexion), making it difficult to swing the leg forward in walking. Foot-drop caused by damage to the central nervous system (rather than to the peripheral nerve which controls the lower leg dorsiflexor muscles) can be alleviated by electrically stimulating the peroneal nerve, causing the lower leg dorsiflexor muscles to contract. Stimulation may be caused through the skin (transcutaneous stimulation) or via an implanted stimulator (subcutaneous stimulation). To cause contraction of the dorsiflexor muscles during the swing phase of gait only, a sensor is used to detect this phase. The sensor is typically a switch located under the heel inside the shoe. The switch is connected to an electrical stimulator on or under the surface of the leg.
A conventional unit for the treatment of foot-drop comprises a heel sensor, a controller and an electrical stimulator. The heel sensor, the controller and the electrical stimulator are connected by wires.
The present inventors have described in an earlier published patent application (WO01/60445) a unit for the treatment of foot-drop wherein the heel sensor and electrical stimulator communicate via a radio transmitter and receiver. In a preferred embodiment, an implanted multi-channel stimulator activates foot lift by stimulating the common peroneal nerve above the knee. The stimulation activates the dorsiflexors which lift the foot. The stimulating electrode is located under the skin just above the knee while the stimulator is located under the skin on the thigh. The stimulating electrode and stimulator are implanted by surgery under local anaesthesia. The implanted stimulator is controlled by an external control unit. The control unit transmits energy and control signals into the stimulator using a wired connection to a lightweight transmitting coil located on the skin over the implanted stimulator. The stimulation is activated by a wireless heel switch located in the shoe. The multiple channels of stimulation make it possible for the clinician to adjust the movement of the foot to ensure a balanced foot lift even when the device has been implanted for a period of time.
In devices such as this, the transmitting coil must be mounted on the skin. This can be achieved using an adhesive Velcro® pad which is attached to the skin, to which the transmitting coil is mounted using a cooperating Velcro® pad.